[ClusterLabs] constraining multiple cloned resources to the same node

[john tillman]

> On 15.03.2022 19:35, john tillman wrote:
>> Hello,
>>
>> I'm trying to guarantee that all my cloned drbd resources start on the
>> same node and I can't figure out the syntax of the constraint to do it.
>>
>> I could nominate one of the drbd resources as a "leader" and have all
>> the
>> others follow it.  But then if something happens to that leader the
>> others
>> are without constraint.
>>
>
> Colocation is asymmetric. Resource B is colocated with resource A, so
> pacemaker decides placement of resource A first. If resource A cannot
> run anywhere (which is probably what you mean under "something happens
> to that leader"), resource B cannot run anywhere. This is true also for
> resources inside resource set.
>
> I do not think pacemaker supports "always run these resources together,
> no matter how many resources can run".
>


Huh, no way to get all the masters to start on the same node.  Interesting.

The set construct has a boolean field "require-all".  I'll try that before
I give up.

Could I create a resource (some systemd service) that all the masters are
colocated with?  Feels like a hack but would it work?

Thank you for the response.

-John


>> I tried adding them to a group but got a syntax error from pcs saying
>> that
>> I wasn't allowed to add cloned resources to a group.
>>
>> If anyone is interested, it started from this example:
>> https://edmondcck.medium.com/setup-a-highly-available-nfs-cluster-with-disk-encryption-using-luks-drbd-corosync-and-pacemaker-a96a5bdffcf8
>> There's a DRBD partition that gets mounted onto a local directory.  The
>> local directory is then mounted onto an exported directory (mount
>> --bind).
>>  Then the nfs service (samba too) get started and finally the VIP.
>>
>> Please note that while I have 3 DRBD resources currently, that number
>> may
>> increase after the initial configuration is performed.
>>
>> I would just like to know a mechanism to make sure all the DRBD
>> resources
>> are colocated.  Any suggestions welcome.
>>
>> [root at nas00 ansible]# pcs resource
>>   * Clone Set: drbdShare-clone [drbdShare] (promotable):
>>     * Masters: [ nas00 ]
>>     * Slaves: [ nas01 ]
>>   * Clone Set: drbdShareRead-clone [drbdShareRead] (promotable):
>>     * Masters: [ nas00 ]
>>     * Slaves: [ nas01 ]
>>   * Clone Set: drbdShareWrite-clone [drbdShareWrite] (promotable):
>>     * Masters: [ nas00 ]
>>     * Slaves: [ nas01 ]
>>   * localShare    (ocf::heartbeat:Filesystem):     Started nas00
>>   * localShareRead    (ocf::heartbeat:Filesystem):     Started nas00
>>   * localShareWrite   (ocf::heartbeat:Filesystem):     Started nas00
>>   * nfsShare      (ocf::heartbeat:Filesystem):     Started nas00
>>   * nfsShareRead      (ocf::heartbeat:Filesystem):     Started nas00
>>   * nfsShareWrite     (ocf::heartbeat:Filesystem):     Started nas00
>>   * nfsService  (systemd:nfs-server):    Started nas00
>>   * smbService  (systemd:smb):   Started nas00
>>   * vipN      (ocf::heartbeat:IPaddr2):        Started nas00
>>
>> [root at nas00 ansible]# pcs constraint show --all
>> Location Constraints:
>> Ordering Constraints:
>>   promote drbdShare-clone then start localShare (kind:Mandatory)
>>   promote drbdShareRead-clone then start localShareRead (kind:Mandatory)
>>   promote drbdShareWrite-clone then start localShareWrite
>> (kind:Mandatory)
>>   start localShare then start nfsShare (kind:Mandatory)
>>   start localShareRead then start nfsShareRead (kind:Mandatory)
>>   start localShareWrite then start nfsShareWrite (kind:Mandatory)
>>   start nfsShare then start nfsService (kind:Mandatory)
>>   start nfsShareRead then start nfsService (kind:Mandatory)
>>   start nfsShareWrite then start nfsService (kind:Mandatory)
>>   start nfsService then start smbService (kind:Mandatory)
>>   start nfsService then start vipN (kind:Mandatory)
>> Colocation Constraints:
>>   localShare with drbdShare-clone (score:INFINITY)
>> (with-rsc-role:Master)
>>   localShareRead with drbdShareRead-clone (score:INFINITY)
>> (with-rsc-role:Master)
>>   localShareWrite with drbdShareWrite-clone (score:INFINITY)
>> (with-rsc-role:Master)
>>   nfsShare with localShare (score:INFINITY)
>>   nfsShareRead with localShareRead (score:INFINITY)
>>   nfsShareWrite with localShareWrite (score:INFINITY)
>>   nfsService with nfsShare (score:INFINITY)
>>   nfsService with nfsShareRead (score:INFINITY)
>>   nfsService with nfsShareWrite (score:INFINITY)
>>   smbService with nfsShare (score:INFINITY)
>>   smbService with nfsShareRead (score:INFINITY)
>>   smbService with nfsShareWrite (score:INFINITY)
>>   vipN with nfsService (score:INFINITY)
>> Ticket Constraints:
>>
>> Thank you for your time and attention.
>>
>> -John
>>
>>
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